1. Field of the Invention
The presently disclosed subject matter relates to an image recording apparatus which corrects density unevenness in an image, and a control method and a program thereof.
2. Description of the Related Art
There has been known an ink-jet recording apparatus (an image recording apparatus) which forms an image on a recording medium by ejecting ink from a plurality of ink-ejecting nozzles (simply referred to as a nozzle below) provided on an ink-jet head. In the ink-jet recording apparatus, density unevenness may occur in the recorded image due to variations in ejection properties (recording properties) of the respective nozzles of the ink-jet head. Thus, an ink-jet recording apparatus according to Japanese Patent Application Laid-Open No. 2010-082989 performs so-called density unevenness correction in which a correction value for the output density of each nozzle (a look-up table or the like) is obtained based on the ejection property of each nozzle obtained by outputting and analyzing a density correcting test chart, and ink ejection from each nozzle is controlled based on an image signal corrected according to the correction value.
In an ink-jet recording apparatus, there is generated a non-ejection nozzle which cannot eject ink due to clogging or breakdown over time. When the non-ejection nozzle as described above is generated, stripe unevenness (a white stripe or a white-black stripe) caused by the non-ejection nozzle occurs in a single-pass-type ink-jet recording apparatus when a recorded image is observed. Thus, an ink-jet recording apparatus according to Japanese Patent Application Laid-Open No. 2012-071474 performs so-called non-ejection correction in which ink ejection from a defective nozzle is prohibited, and the output densities of adjacent nozzles adjacent to the defective nozzle are increased.
The stripe unevenness is caused not only by the non-ejection nozzle described above, but also by a “largely-deflected nozzle” having a large amount of ink flight deflection. As a first correction method for correcting the stripe unevenness caused by the largely-deflected nozzle, a method for performing the density unevenness correction described in Japanese Patent Application Laid-Open No. 2010-082989 in a state in which ink ejection from the largely-deflected nozzle is continued is employed. As a second correction method, a method for performing the non-ejection correction described in Japanese Patent Application Laid-Open No. 2012-071474 in which the output densities of adjacent nozzles adjacent to the largely-deflected nozzle are increased. However, in an ink-jet recording apparatus in which the density unevenness correction and the non-ejection correction are both employed, overlapping correction (also referred to as overcorrection) may occur when the density unevenness correction and the non-ejection correction are applied in an overlapping manner.
In an ink-jet recording apparatus according to Japanese Patent Application Laid-Open No. 2010-188663, when a defective nozzle such as a largely-deflected nozzle is generated, a correction value for correcting density unevenness is modified by changing density measurement values of the defective nozzle and adjacent nozzles by use of density measurement values of surrounding nozzles that are not affected by the defective nozzle. Subsequently, the ink-jet recording apparatus executes density unevenness correction based on the modified correction value, and non-ejection correction. That is, in the method according to Japanese Patent Application Laid-Open No. 2010-188663, the priority of the density unevenness correction is decreased, and the priority of the non-ejection correction is increased.